Tendrils of Terrorism Spread Through Southeast Asia After Jakarta Attack

A younger generation of terrorists graduates in Indonesia's radical heartland. Solo, a small city in central Java, has been a center of Islamic militancy and appears to be linked to recent terrorist attacks. (Photo: Kartika Bagus Cahyono)

JAKARTA, Indonesia—Indonesian police said they are chasing down more terrorist cells in the country as they expand their investigation into a deadly attack linked to Islamic State in the capital last week.

Malaysian police, meanwhile, said they thwarted a potential terrorist attack when they arrested a 28-year-old Malaysian man carrying a weapon and documents relating to Islamic State at a suburban train station near Kuala Lumpur on...